With reference to FIG. 1, a conventional boost circuit for driving a backlight module of a liquid crystal display device mainly has an input power Vin, a first winding L1 connected to the input power Vin, a diode D1 connected between the first winding L1 and an output capacitor, and a transistor switch Q1 connected between the first winding L1 and the diode D1.
The boost circuit uses the action of repeatedly switching on-and-off of the transistor switch Q1 to control the first winding L1 to output a forward voltage, and then to charge the output capacitor together with input power Vin, so that the output capacitor can provide an output voltage Vo higher than the input voltage Vin to the backlight module on a load end.
Foregoing boost circuit implements a boosting effect that the output voltage is higher than the input voltage. However, since the boost circuit uses the diode D1 for rectification, as the circuit outputs a large current, power consumption of the diode on reification will become extremely large and cause the efficiency of the boost circuit to decrease and has a problem of heat dissipation. If the boost circuit uses a MOSFET for rectification, the circuit needs to be driven with a floating ground isolation, which causes design of the circuit to be more complicated.
Hence, it is necessary to provide a self-driven synchronous rectification boost converter to overcome the problems existing in the conventional technology.